Particle-induced coating defects
Investigations on the vacuum arc evaporation behavior of modified graphite cathodes and influence on the particle-induced defects in deposited (t)a-C coatings with and without dopant elements
Due to their high specific strength and good machinability and recyclability, aluminum alloys are attractive lightweight construction materials, especially for structural components in the automotive and aerospace industries. However, the low hardness and thus limited wear resistance as well as the sometimes unfavorable friction behavior severely limit the use of Al alloys for components with tribological functional surfaces. DLC coatings, on the other hand, are excellently known as tribological protective coatings on components subject to friction and wear. However, as they have practically no supporting effect due to their low thickness, their use on the comparatively soft aluminum materials is not appropriate.
In this project, electron beam surface layer treatment with an additive (EB remelt alloying) is used to develop suitable supporting intermediate layers that form a suitable basis for resistant DLC layers. The phenomena of coating failure are investigated using classical methods of adhesive strength measurements and specially adapted characterization techniques such as pop-in nanoindentation (see Figure 1), and evidence of an optimized supporting effect of the EB intermediate layers is provided.
Figure 1
Figure 1. Particle emission during arc discharge of a graphite cathode (left), SEM cross-section of a ta-C film with particle-induced film defects (center) and growth of two particle-induced film defects in ta-C made visible by means of alternating Cr interlayers (right).